OK...In No. VA, I love Lebanese Taverna (5900 Washington Blvd., Arlington, VA). While not a strictly vegetarian restaurant, it has lots of vegetarian offerings. The meat dishes are delicious so there is something for everybody! Gotta love that!
In DC, if you are looking for a swanky dining-out option, there is Restaurant Nora (2132 Florida Avenue, NW, WDC). I think it was the first restaurant to be designated as organic. They too serve meat, but also lots of veggie options. Very expensive, tho.
Also in DC is Yanyu (3435 Connecticut Ave., NW, WDC). I would call what they serve "Eurasian." They have a totally awesome vegetarian tasting menu.
In MD, there is the Vegetable Garden (11618 Rockville Pike, Rockville, MD). It is chinese vegetarian and is terrific. The food is delectable and very creative. Prices are great, too. See my post in the Side Orders>Mushrooms thread.
Lastly, in MD, there is the Olney Ale House (2000 Olney-Sandy Spring Rd., Olney, MD). It is a beer garden with great vegetarian options.
Meowzart--not a vegetarian, but loves food in all its forms